The present invention relates to apparatus for applying a liquid to a sheet of material, in general, and to such apparatus for applying a liquid developer to a surface of a film unit or sheet of photosensitive material, in particular.
The use of small volumes of processing liquids has become particularly important in connection with instant image processes where image development is carried out immediately after exposure of a photographic film or immediately after a previously exposed film is withdrawn from a light-tight cassette and where small volumes of processing liquids must be employed for proper image development. If an excessive amount of processing liquid is applied to a sheet of photosensitive material in such circumstances, it will produce an undesirable or negative effect on overall image quality.
Instant image processing is very often accomplished by squeezing a processing fluid out of a rupturable container or pod by drawing the processing fluid containing pod between a pair of adjacent pod-rupturing and fluid-spreading rollers. After the pod has been so ruptured, its contents are squeezed out and then evenly spread between adjacent photographic film layers for film developing purposes. This type of spread system is capable of accurately spreading a fairly precise thickness of developer fluid between such adjacent layers for proper image development. However, a spread system of this type is relatively expensive because it requires the use of precisely dimensioned spread control components (e.g., precision rollers) in order to achieve such fluid-thickness distribution.
In another presently available spread system, processing fluid is applied to a surface of a sheet of photosensitive material by means of a pad-type liquid applicator. Processing fluid spreading is accomplished by establishing contact between a coated surface of the photosensitive material and a spreading element or applicator pad consisting of any of a variety of flat, porous capillary action materials impregnated with processing fluid. These fluid-spreading elements are porous structures in the form of individual sheets which may be woven or non-woven webs of paper, porous plastic or metal layers, sponge or foam-like material or hydrophillic material if an aqueous processing fluid is employed. The fluid-spreading element may be presoaked with sufficient liquid to process a single photosensitive sheet or may be provided in combination with a container of liquid that serves as a reservoir for providing additional liquid when the required volume of liquid for complete processing exceeds the liquid holding capacity of the fluid spreading element.
An applicator pad processing liquid spread system is less costly than the spread roller spread system mentioned above primarily because of the absence of the need for precisely dimensioned components that are relatively expensive to manufacture. However, applicator pad spread systems often require the use of squeegee-like devices to insure complete contact between the pad and the surface of the sheet of material to be coated. In addition, applicator pad type spread systems tend to be bulky and as presently constructed are incapable of simultaneously spreading process fluid on both sides of a sheet of photosensitive material.
A primary object of the present invention, therefore, is to provide a method and apparatus for simultaneously coating both sides of a film unit or sheet of photosensitive material.
Another object of the present invention is to provide a method and apparatus for readily coating the surface of a series of individual sheets of photosensitive material.
Yet another object of the present invention is to provide a method and apparatus for insuring complete contact between a fluid-spreading applicator pad and a coated surface of a sheet of photosensitive material.
A further object of the present invention is to provide a portable applicator pad type processing fluid spread system of minimum size.
Other objects, features and advantages of the present invention will be readily apparent from the following detailed description of the preferred embodiment thereof, taken in conjunction with the accompanying drawings.